It is known that there is a cooling plant in every portable air conditioner, and it is also known that the cooling gases coming from the compressor must then be cooled in a condenser so that, during evaporation, they are able to absorb heat and thus allow the air conditioner to perform its function.
By conditioners here we mean in particular domestic conditioners, or for rooms, more advantageously we mean portable air conditioners as indicated above.
In this type of conditioner, it is important to obtain the best performance without having to increase the external sizes of the conditioning unit, and indeed doing as much as possible to reduce it, since in any case the conditioner constitutes an encumbrance.
In cooling plants for this type of conditioner, the temperature of the cooling gases that enter the condenser is on average around 70° C., while exiting from the condenser the temperature is around 55° C. The air exiting from the condenser has a temperature around 50° C. and is sent outside by means of a suitable hose or other suitable system.
In the state of the art, some solutions are known concerning small air conditioning devices in which solutions have been used to improve cooling efficiency of a compression cooling cycle.
U.S. Pat. No. B5,031,690 describes a portable air conditioner for cooling an aircraft when it is on the ground, which provides a refrigerating circuit comprising two condensers connected in parallel with respect to the circuit of the cooling fluid. Each condenser, due to the position it assumes in the circuit, is hit by a different and distinct stream of air, because the two condensers are disposed co-planar with respect to each other. This solution does not allow to reduce the absolute condensation pressure, nor therefore the compression work, so that the increased efficiency obtained is limited.
The patent application US-A-2005/0028545 describes a refrigerating circuit to be applied to a conditioning plant for a civil structure which, in one embodiment, provides a pre-cooler located in series and upstream of the condenser. In this case too, due to their reciprocal position in the circuit, the stream of air that hits the pre-cooler is not the same that hits the condenser, and therefore the desired increase in efficiency is not obtained in terms of reducing the compression work.
Due to the circuit configuration the system described here is not suitable for use in a portable air conditioner for domestic use.
The patent application EP-A-1,068,967 describes a refrigerating circuit for an air conditioning apparatus for a motor vehicle that provides a condenser preceded by an auxiliary exchanger. In correspondence with the auxiliary exchanger a heat exchanger is provided between two liquid substances. Therefore, in this case too no single stream of air is provided that exchanges heat first with the condenser and then with the auxiliary exchanger.
These prior art documents describe applications of a refrigerating circuit that do not allow to solve the problems found in a domestic portable air conditioner, in which there is a need to improve the efficiency of the refrigerating circuit considering the limits imposed by the bulk, weight and industrialization requirements of the production process.
The patent application FR-A-2,305,699 describes perfected installations that provide a heat pump circuit. The heat pump circuit provides a recovery exchanger connected in series to the condenser, both are hit by a stream of air and with respect to this the recovery exchanger is located upstream of the condenser.
The patent application FR-A-2,439,371 describes a heat pump circuit with heat exchange between two liquid substances. The circuit does not provide the presence of an auxiliary exchanger connected to the condenser.
The present Applicant has studied the problem of increasing the efficiency of cooling units for this type of portable air conditioner, maximizing the heat exchange between the air and the coolant before the coolant enters the condenser, without requiring an increase in the external sizes of the conditioner, and indeed possibly reducing them, hence without modifying the bulk and external shape of the portable air conditioner.
He has also studied the problem of increasing the efficiency of cooling units without modifying the sizes and conventional position of current components, and thus being able to keep substantially unchanged the structure and internal configuration of conditioners currently produced.
The purpose of the present invention is therefore to improve the performance of a cooling unit for portable air conditioners of the type identified above, without affecting the external sizes and geometry of the conditioner and the configuration and disposition of the internal components.
Another derived purpose is to apply this improvement to portable air conditioners already on the market as well, with a limited modification in the production line and with a limited expense, increasing their thermal yield.
Another purpose is to increase the cooling power obtained, with the same power absorbed by the machine.
The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.